I don't think Hasan ignored the distinction. He addressed it directly.
His point wasn't that "lots of civilians died, therefore genocide." His point was that genocide requires intent to destroy a protected group
Not a "protected" group - any group, Germans or Russians or Galactic Imperials, whoever. It only counts if you are deliberately killing your targets because of their identity.
He argues the Allies were trying to defeat Germany, not destroy Germans as a people. Whether you agree with that or not, that's the distinction he's making.
Quoting Patton or Arthur Harris saying awful things doesn't automatically prove the Allies intended to wipe out the German people. It proves they were willing to use brutal tactics and that some leaders used hateful rhetoric. That's evidence you could use in a war crimes argument. It's not automatically evidence of genocide.
So if you think the Allied bombing campaign and Gaza are legally the same, then make that case. Show that the Allies intended to destroy the German people as a protected group. Just saying "they bombed civilians too" skips over the part Hasan is actually arguing about.
You can disagree with Hasan's conclusion, but saying he never drew a distinction isn't really true.
Allied bombings and Gaza are the same, in that neither are genocide. Patton, Harris, etc., all spoke the same way Ben-Gvir or Smotrich do. Israel does not intend to destroy Palestinians as a group and has not been moving towards destroying Palestinians as a group - instead they have been negotiating ceasefires, providing warnings before bombings, advising civilians to flee, leaving refugee corridors open, etc. This is not mutually exclusive with a high, horrible civilian death count, or committing war crimes all the while; it is exclusive with intentionally trying to exterminate a people. You can charge people with all sorts of awful crimes through accidents or negligence or disregard, but you can't charge them with genocide for it. This is also why there are first, second, and third degrees of murder, then manslaughter, then negligent homicide, then self-defense, etc.
Hasan draws a distinction by seeming to admit that Stephens is correct about Allied brutality, but not daring to engage directly with Stephens' question about how someone can claim there was a Palestinian genocide but not a German one.
Read the transcripts of the Nuremberg trials provided here. One Nazi Einsatzgruppen commander after another showed up sounding just like Mehdi Hasan - "Your weapons are so much more powerful, you butchered our children from the air by the tens of thousands" - and one after another, the judges had them silenced by the rope. I can highlight the most important segments but it would be best if you (or anyone else interested) gave it the full read on your own and really thought about it, slept on it.
A false equivalence has Nazi precedents.
martinkramer.org
We have also previously discussed here that under international law, all war crimes are equally severe, genocide is not the final boss of war crimes, yet it is one of the hardest to prove - so why the special desperation to prove that one, and not others that they could pin on Israel so much more easily, or unquestionably? Instead of nailing an open-and-shut case of Israel cutting off civilian electricity supply, its adversaries are trying revise the definition of genocide specifically to make sure Israel is found guilty of it. This plainly strips the whole concept of any moral meaning and had better not be endorsed by anyone who has a problem with Ron DeSantis calling all openly gay teachers "groomers".